I'm driving to a friend's house next week. It is 104 miles. I will start at sea level, go up to 4000 feet and back down to about 2000 feet. The return trip I would really like to take would be from his house up to 8000 feet and back to my house at a distance of 153 miles. An intermediate return route would go from 2000 feet up to 7000 feet in 143 miles. I went on a drive this past weekend of 150 miles and I returned with an ideal range of 54 miles remaining. About half of that drive was on the freeway at 75 mph with maybe 1000 feet of elevation gain. So, how much can I expect elevation to affect my range?